1. Technical Field
The invention relates to semiconductors and the fabrication thereof. In particular, the invention relates to lithography used to define one or both of micro-scale and nano-scale structures during semiconductor fabrication.
2. Description of Related Art
Photographic contact lithography and imprint lithography are examples of two lithography methodologies for defining micro-scale and nano-scale structures that generally involve direct contact between a patterning tool (e.g., mask, mold, template, etc.) and a substrate on which the structures are to be fabricated. In particular, during contact lithography, the patterning tool (i.e., mask) is aligned with and then brought in contact with the substrate or a pattern receiving layer of the substrate. Similarly, in imprint lithography, the patterning tool (i.e., mold) is aligned with the substrate after which the pattern is printed on or impressed into a receiving surface of the substrate. With either method, alignment between the patterning tool and the substrate general involves holding the patterning tool a small distance above the substrate while lateral and rotational adjustments (e.g., x-y translation and angular rotation) are made to a relative position of one or both of the tool and the substrate. The patterning tool is then brought in contact with the substrate to perform the lithographic patterning.
In both of contact lithography and imprint lithography, an ultimate 5 alignment accuracy as well as an achievable patterning resolution may be affected by a degree to which the patterning tool and substrate are both mutually parallel and proximal during the alignment process. In addition, accuracy and resolution depend on maintaining an achieved alignment during contact lithography. In particular, accuracy and resolution may suffer as a result of drift or slip in the relative positioning of the aligned patterning tool and substrate that may occur as the tool is brought into contact with the substrate following an initial alignment.
Furthermore, thermal gradients (both static and dynamic) as well as mechanical and acoustic vibration often lead to or result in thermo-instability and/or vibrational instability during contact lithography. Thermo-instability and vibrational instability can further degrade or otherwise adversely affect one both of the ultimate alignment accuracy and the achievable patterning resolution.